The U.S. Environmental Protection Agency (EPA) has adopted a comprehensive program to reduce emissions from future off-highway vehicles. The EPA's Interim Tier 4/Stage III B emissions regulations call for a 90 percent reduction in particulate matter (PM) and a 50 percent drop in nitrogen oxides (NOx). The EPA's Final Tier 4/Stage IV emissions regulations, which may be fully implemented by 2015, are expected to take PM and NOx emissions to near-zero levels.
Advanced exhaust treatment systems are needed to satisfy the EPA's emissions regulations. Such exhaust treatment systems must be reliable to maintain continued compliance with the EPA's emissions regulations. If one part of an exhaust treatment system were to fail, a leak could develop, causing the exhaust treatment system to fall out of compliance with the EPA's emissions regulations.